Re: Low loss core material

What about Philips 3C94, ~ 75kW/m3

Cheers

-- Cheers, James Arthur

Can you use any of the amorphous materials?

How does coercivity affect the core losses while operating at low B? Or, does increasing frequency 'negate' the hysteresis losses?

"Phil Allison"

Posting much to late in my excuse.

..... Phil

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We can use any material, as long as it can be shaped as a toroid. We will use custom tools in collaboration with the ferrite manufactor to give us the desired shape.

We really haven't found any information on how coercivity affects the losses, except for a measurement that showed that high-coercivity material seemed to have low losses. Perhaps someone here has info on that subject?

Thanks

Klaus

Thanks, it looks like a good candidate :-)

Figure 6 stops at 80mT. Is the curve straight all the way down, or is there er curving effect at lower flux densities?

Thanks

Klaus

You might look at nickel-zince ferrites - lower permeability, but higher electrical resistance than regular manganese-zinc ferrites. They are typically used at frequencies above 1MHz, but if you want very low loss at 100kHz one of them might be worth a look.

Ferroxcube list a bunch of materials. The .pdf is large - 7.3M - and horribily inaccessible, like every other Ferroxcube document.

EPCOS offers a few NiZn ferrites - M13 might be interesting, but their literature isn't much more helpful

-- Bill Sloman, Nijmegen

I would say that those are normal operating ranges. eg tested values. You could linear interpolate the lower numbers your looking for, but the core material may be a curve at those levels. I don't see any App notes related to your question. I suggest you give one of their application engineers a call.

Cheers

And also call one of the smaller places, like the one in my other post. Small is often better because they are more flexible. Just had that happen with a small motor manufacturer where, to my utter surprise, they offered to do a little redesign on the commutator and brushes for us.

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That sounds backwards, unless the measurement was boscured by including ALL losses. High-coercivity material should have higher hysteresis loss. Coercivity is like friction, subtracts off the A/m no matter which direction you're going. So, like friction, it subtracts off the drive and there is a loss each cycle.

Do you have your heart set on 100kHz? At 50kHz you could use a roll of 0.5 mil metglas rolled into a torroid. coercivity is about 1/10 any other materials. The permeability, I've measured at 1,000,000 [pretty much a dead magnetic short] at 50kHz you'll still measure permeability at around 40,000.

Thus, the ONLY loss you'll get in your core will be the resistive eddy current losses.

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Nice. Never knew there was such a material. Found a price on

Not that expensive :-)

Thanks

Klaus

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the original source was out of New Jersey, then the compnay was sold, resold, etc. I vaguely remember it was owned by Honewell, Mitsubishi, etc.

It is my understanding the original practical manufacutring process for making this material, which is cooled at over 1,000,000 C/sec came from a man by the name of Akira Hasegawa. The process uses RF plaxma to spray molten material onto a nearby spinning cylinder [cooled with liquid nitrogen] The material follows the cylinder for a bit then is taken off to a take up reel. In something like 40 seceonds you can have 10 miles of this stuff on the take up reel. I heard that the speed is near the speed of sound so production floor has dramatic sound effects, and worse any slip up means a LOT of material lying all over the place.

Also, check for metglas competitors under the heading of 'amorphous' material. I think there are some sources out of Asian rim that probably cost far less.

You never said how much power you were trying to transfer. Maximum widths are on the order of 6 inches. And you can't do much 'work' to the material, almost everything you do deteriorates the properties.

For me, the downsides were the low Bsat, 0.9 to 1T, and the fairly high conductivity, on the order of 0.7 MS/m

But you should see the specs you can get, and the dynamic range you can get if you use the material to make an audio transformer!

Two important points if you get samples. Although metal and looks like foil, it's brittle and will shatter like a ceramic. The edges are RAZOR sharp. Colleague got a 'paper' cut, didn't know it until he was dripping blood on the project. And the oily film contaminated the cut making it SLOW to heal. Oh, yeah, having a lot of iron content, it will rust, keep it in a sealed package with a desicant. Try experimenting with it.

Look forward to hearing about what you come up with.

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Great info, thanks. We are making highly linear power supplies, half bridge, no output inductance, full conduction angle, which is referred to DC transformers. They are used to provide isolation across a barrier.

We transmit only 600mW, but are looking for losses below 1mW in the midrange power level. We are close now with a better grade material, but for future project we would like to have a cutting edge technology, which could boost specs in other areas.

You mention audio transformers with good dynamic range, and that what we want, translates to good liniarity and low losses

The datasheet:

Defines annealed permeability of 600k, while cast is only 45k. Annealing is a heat treatment, while casting is I guess a mold, so the material can be shaped in any custom shape. Annealing can probably only be shaped in a minor way to a custom shape without degrading the permeability significantly. Any insights on those specific specs in the datasheet?

Regards

Klaus

I heard, second hand, that some properties are not that stable. I think it was permeability, but I can't say for sure. ( it might even have to do with the core heating and changing its properties) I would have mentioned Metglas, but I didn?t want you to inherit a headache. It's more expensive, and harder to work with. but I'm sure there are success stories in the high power transformer areas.

Cheers

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The amorphous materials tend to have high aging problems, loss of permeability over 100days in the region of 50% reduction. nanocrystaline materials have low aging effects, whereas amorphous have high aging effects

As for gapping a high u core, keeping the turns the same as a low u core, I cannot find any information that can determine the reduction in core losses due to gapping. Anyone?

Lets say I have two cores of identical volume, but different materials. Core 1 has permeability of 1000, core 2 has 10.000. I use the same number of turns on both cores, and I want the same inductance, so I gap core 2 with high permeability to get the same effective permeability as core 1. So they end up with the same Al value and the same inductance.

What is the difference of core losses if we assume the loss equation, Steinmetz is the same? (Pv =3D n * f^a * B^b)

Ofcourse gapping causes fringing eddy current losses, but for simplicity those losses are ignored....

Thanks

Klaus

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If - and it's a big if - the loss is due to eddy current circulating in the core, the gap won't make any significant difference.

Each core represents a single turn of - slightly - conductive material, and the voltage generated around that single turn will be the same, so the current circulating will be determined only by the resistance of the core material.

The higher resistance material will have less circulating current and the power loss will just be the single-turn voltage multiplied by the current, which is to say that the higher resistance material will have a lower core loss.

In fact the core could be divided into a series of concentric shells, each one with a short current path and a lower induced voltage, but this wouldn't make any difference to the result.

-- Bill Sloman, Nijmegen

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I don't trust 'packaged' formulas, unless I check their derivation. To compare what you just described, including the assumptions, I'd use a finite element solver, like free femm 4.2 For me, VERY accurate. and relative calculations I've confirmed down into the ppm accuracy.

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Shifting permeability was no problem for us. 0.005 to 0.010% just did not affect the performance

Again, this stuff is AMORPHOUS Bending destroys it. Drilling destroys it...Looking at it cross eyed destroys it.

Even gently rolling the material into a torroid shape shifts the characteristics.

From memory, there were very specific rules as to how to 'adjust' the material's electrical characteristics.

Remember amorphous is amorphous the manufacturing process MAKES it amorphous, and anything you do later undoes the amorphous. Unless you can cool at 1,000,000 C per second.

Don't these people make the torroids up for you? at 600mW, that's a small size. But they all have built in air gap. If you can live with no air gap, look for the square hysteresis cores. You can always put a small bias in to keep them centered in the hysteresis curve. The transfer when you do that is INCREDIBLE.

I once used the material's square hysteresis characteristic when there's NO gap to make simple isolating transformers for the spectrum of DC-1kHz Cost was less than $.30 per isolation, and we're talking UL accepted 3kV power isolation specs.

For audio transformers: Dynamic range when used in an audio transformer is due to the extremely low coercivity. Unlike most materials, it does NOT require energizing. It's just a dead magnetic short.

Are you doing synchronous/ideal diode rectification?